Opposed piston multicylinder engine

ABSTRACT

DISCLOSED HEREIN IS AN ENGINE CONSTRUCTION FOR A FAMILY OF LIGHTWEIGHT AND COMPACT INTERNAL COMBUSTION ENGINES WHICH CAN HAVE 4 OT 8 OR MORE CYLINDERS. THE ENGINE CRANKCASE IS GENERALLY IN A FORM OF A SQUARE PRISM WITH TWO CRANKCASE SECTION WHICH ARE CAST FROM THE SAME MOLD, AND WHICH ABUT ALONG A DIAGONAL INTERFACE WITH   EXTENDS THROUGH THE AXIS OF ROTATION OF THE CRANKSHAFT. PAIRS OF OPPOSITELY ACTING PISTONS ARE ARRANGED AROUND THE FOUR FACES OF THE PRISMS. THE PISTONS RECIPROCATE IN CYLINDERS WHICH ARE SECURED TO THE CRANKCASE FACES.

Sept 20 1971 K. F. zlEGLER 3,605,705

OPPOSED PISTON MULTICYLINDER ENGINE Filed July e, 1969 5 sheets-sheet 1 Sept. Z0, 1971 K. F. zlEG LER 3,605,705

OPPOSED PISTON MULTICYLINDER ENGINE Filed July 8, 1969 5 Sheets-Sheet 2 Sept. 20, 1971 K. F. zlEGLER 3,605,705

OPPOSED PISTON MULTICYLINDER ENGINE Filed July 8, 1969 5 Sheets-Sheet 3 /omeyr Sept. 20, 1971 K. F. zlEGLl-:R 3,605,705

oPPosED PIsToN MULTICYLINDER ENGINE Filed July 8, 1969 5 Sheets-Sheet 4 Sept. 20, 1971 K. F. zlEGLER OPPOSED PISTON MULTICYLINDER ENGINE 5 Sheets-Sheet 5 Filed July 8, 1969 /nz/ea/or 217'( Y. Je /cr j/ jf WM, MM, Mm Mw@ @rzeg GNN United States Patent O 3,605,705 OPPOSED PISTON MULTICYLINDER ENGINE Kurt F. Ziegler, Zion, Ill., assignor to Outboard Marine Corporation, Waukegan, Ill. Filed July 8, 1969, Ser. No. 839,832 Int. Cl. F0211 75/22, 75 /24; F01b 1/06 U.S. Cl. 12S-55A 15 Clalms ABSTRACT OF THE DISCLOSURE Disclosed herein is an engine construction for a family of lightweight and compact internal combustion engines which can have 4 or 8 or more cylinders. The engine crankcase is generally in a form of a square prism with two crankcase sections which are cast from the same mold, and which abut along a diagonal interface Iwhich extends through the axis of rotation of the crankshaft. Pairs of oppositely acting pistons are arranged around the four faces of the prism. The pistons reciprocate in cylinders which are secured to the crankcase faces.

BACKGROUND OF THE INVENTION The invention relates to internal combustion engines and more particularly to an engine construction for a family of engines.

'SUMMARY OF INVENTION The invention provides a novel crankcase and cylinder arrangement which can be utilized to provide a family of lightweight, compact internal combustion engines, which can have four or eight or more cylinders and which can be air cooled or water cooled. Various of the advantages of the invention can also be obtained in a two cylinder engine. The use of pairs of opposed oppositely acting pistons provides an inherently balanced engine which is essentially vibrationless.

The overall length or height of the engine is minimized by arranging the pairs of opposed oppositely acting pistons for reciprocation about axes normal to the four faces of a crankcase having the configuration of a square prism. For instance, in a four cylinder engine there is a piston reciprocating along an axis perpendicular to each of the four crankcase faces. The opposed pistons in each pair are located in separate cylinders in cylinder members secured to opposed crankcase faces. The axes of reciprocation of the pistons are spaced at varying distances from one end of the crankcase to afford connection to spaced crankpins on the crankshaft. The overall length of the crankcase of a four cylinder engine in accordance with the invention is less than the `total diameter of three pistons.

The engine crankcase is formed =with two identical crankcase sections, with each section in the form of a triangular or right angle solid which can be diecast in the same mold. The sections are secured together along a diagonally extending interface or plane which extends through the axis of rotation of the crankshaft. Each crankcase section is provided with arcuate walls which complement each other when the sections are secured together to form connecting rod wells, which are common for each pair of opposed pistons and lwhich are isolated from the adjacent connecting rod wells.

The engine crankshaft has a pair of crankpins which are angularly offset at 180 for each pair of opposed pistons. The crankpins for each pair are aligned so that there are only two throws for the crankshaft with the throws offset at 180. The inherent balance resulting from the use of opposed pistons eliminates the need for counterweights which are generally required to balance the crankshaft.

ICC

The invention also provides an arrangement for -securing the engine flywheel to the crankshaft, which arrangement includes a fastener having an exteriorly threaded boss with an axial aperture having an internal spline. The threaded boss is threadably received in a bore at one end of the crankshaft. The fastener is locked in position to thus secure the flywheel to the crankshaft by an external spline on the end of the driveshaft which extends through the aperture in the fastener and into an internal spline in the bore of the crankshaft.

It is an object of the invention to provide an engine configuration for a family of engines of various numbers of cylinders which can be produced with a minimum number of molds at a minimum expense.

It is an additional object of the invention to provide an engine iwith a crankshaft 'which can be machined in a minimum number of machining operations.

A further object of the invention is to provide a crankcase which has two crankcase sections which can be formed from a single mold.

It is a further object of the invention to provide an eight cylinder engine which has a crankcase with a length less than the length of a six cylinder in-line engine having the same piston diameters.

It is an additional object of the invention to provide a family of compact engines in which the length of the crankcase is less than one-half the product of the number of pistons multiplied by the diameter of one piston plus the diameter of one piston.

Further objects and advantages of the present invention will become apparent from the following description and accompanying drawings.

DRAWINGS FIG. l is a fragmentary perspective view with portions removed showing an eight cylinder internal combustion engine in accordance Iwith the invention.

FIG. 2 is a fragmentary side elevation view with portions removed of the engine shown in FIG. 1.

FIG. 3 is an enlarged fragmentary view of a portion of the crankcase and the crankshaft of the engine shown in FIG. 1.

FIG. 4 is an enlarged plan view with portions broken away and in fragmentary section of `the engine sho-wn in FIG. l, and rotated from the orientation of the engine shown in FIG. 1.

FIG. 5 is an enlarged sectional view of a cylinder member taken along the line 5-5 of FIG. 1.

FIG. 6 is a sectional view taken along line 6 6 of FIG. 5.

FIG. 7 is a fragmentary sectional view taken along the line 7 7 of FIG. 5.

FIG. 8 is a front perspective view of `the engine shown in FIG. 1, employed in a marine propulsion unit.

FIG. 9 is a side perspective view of the engine shown in FIG. 8.

FIG. l0 is an enlarged fragmentary sectional view of the crankshaft, drive shaft, flywheel and flywheel fastemng arrangement.

FIG. 11 is an exploded fragmentary perspective view of the flywheel fastening arrangement shown in FIG. 10.

DETAILED DESCRIPTION The invention provides a family of compact, lightweight internal combustion engines which utilize two pairs of opposed pistons to provide a vibrationless enigme operation.

Referring to the drawings, FIG. 1 discloses an eight cylinder embodiment of an engine which is in accordance with the invention, which is `generally designated 10, and which comprises a crankcase 12 having first and second symmetrical crankcase half-sections 14 and 16, which can be cast from the same mold or die to substantially reduce the cost of manufacture. Each of the crankcase sections 14 and 16 is generally in the form of a right angle solid and can include a semi-circular ange portion 15 at one end to form a circular pedestal 17 to facilitate mounting of the engine 10. The crankcase section 14 has lirst, second and third angularly related surfaces 18, 20 and 21 respectively, and an upper end wall 22. The crankcase section 16 has first, second and third angularly related surfaces 24, 216 and 27 and an end wall 28. When the crankcase sections 14 and 16 are secured together as hereinafter described, the rst surfaces 18 and 24 of each crankcase section 14 and 16 are in abutting relationship along a plane extending through the axis of a crankshaft 31 and form a crankcase having the general configuration of a square prism extending from a circular pedestal. The faces 20, 21, 26 and 27 comprise the outer faces of the prism.

In the disclosed embodiment for an eight cylinder engine, the crankcase section 14 is provided with four spaced, semi-annular wall portions 32 (FIGS. 3 and 4) and crankcase section 16 is provided with four semi-annular wall portions 36.

When the crankcase sections 14 and 16 are secured together, the opposed annular wall portions 32, 36 complement each other to form connecting rod wells 40. Each of the connecting rod wells is a common reservoir from which a fuel-air mixture is supplied to a pair of oppositely acting pistons as hereinafter described. Each of the four outer faces 20, 21, 26 and 27 of the crankcase sections is provided with two ports 41. Each port 41 communicates with a connecting rod well 40. Thus, each connecting rod Well 40 communicates with two ports 41 located on opposite crankcase faces for receiving connecting rods of opposed oppositely acting pistons. To maintain the desired pressures for fuel intake and fuel ow into the combustion chambers, each connecting rod well 40 is isolated from the adjacent well 40 by seals 50 which are in the form of rings located in annular grooves 50A on the crankshaft 31 (FIG. 3), and which are in sealing engagement with the annular crankcase walls 32, 36. In the disclosed embodiment of an eight cylinder engine the crankshaft only requires three seals 50 which can .be provided to seal the common connecting rod wells 40 from each other. The crankcase 12 is also provided with end seals 43 and support bearings 45.

The disclosed embodiment of the engine includes eight pistons 51, 52, 53, 54, 55, 56, 57 and 58 (FIG. 2). To minimize overall engine length or height and minimize engine vibration, the pistons are arranged in pairs of oppositely acting pistons. The pistons 51 and 52 form a pair 60 of opposed pistons; the pistons 53 and 54 form a pair 62 of opposed pistons; the pistons 55 and 56 form a pair 64 of opposed pistons; and the pistons 57 and 58 form a pair 66 of opposed pistons. As shown in FIG. 2, piston pairs 60 and 62 are in a stacked or superimposed vertical array and pairs 64 and 66 are similarly in a stacked vertical array, which is angularly offset at 90 from the pairs 60 and 62. When the engine is in an upright position with the crankshaft 31 extending in a vertical plane, as shown in FIG. 2, the piston pair 60 is vertically above the other pairs. The piston pair 64 is below the pair 60, the piston pair 62 is below pair 64 and the piston pair 66 is below the pair 62. By arranging the pairs of pistons around the crankcase faces in the manner disclosed, the piston pair 64 overlaps the piston pair 60, the pair 62 overlaps the pair 64 and the pair 66 overlaps the pair 62 to thus provide a compact engine. The overall height or length of the engine can be less than the product of the total number of pistons times the diameter of one piston, this product divided by two, plus the diameter of one piston. Thus the length of an eight cylinder engine is less than the diameter of one piston multiplied by five. The length of a four cylinder engine would be less than the diameter of one piston multiplied by three.

The offset arrangement of the pairs of pistons is facilitated by the use of a novel crankshaft, which has eight crankpins (FIG. 3) 70, 72, 74, 76, 78, 80, 82 and 84. Crankpins 70 and 72 form a pair of crankpins which are angularly offset at 180 and located in one of the four common connecting rod wells 40. The crankpins 70 and 72 are connected to the pistons 51 and 52 by connecting rods 86, which are hereafter described in detail. Crankpins 74, 76 are also offset at 180 and are connected to pistons 55 and 56', crankpins 78, 80 are similarly offset at 180 and connected to pistons 53 and 54. The crankpins 82 and 84 are also offset at 180 and are connected to pistons 57 and 58 by connecting rods 86. As shown in FIG. 3, crankpins 72, 76, 78 and 82 are offset 180 from the crankpins 70, 74, 80 and 84 to provide a crankshaft 31 with only two throws. This arrangement facilitates machining of the crankshaft since each set of four crankpins for a single throw can be machined with the crankshaft mounted for rotation in a single position with respect to the arbor of the lathe. Alternatively, an engine can be constructed with the crankshaft having four throws, i.e., one every This arrangement decreases the time interval between successive power impulses.

Inasmuch as the use of opposed pistons results in an engine which is inherently balanced, the crankshaft does not require counterweights, thus the overall engine weight is decreased and the amount of metal required for the crankshaft is kept at a minimum to reduce manufacturing costs.

To minimize the width and weight of the crankcase 12 and reduce the volume of the connecting rod wells 40, each connecting rod 86 has a bearing 88, which is split into two bearing portions 90 and 92, which abut along an interface which is at an angle of 45 relative to the longitudinal axis of the connecting rod 86. The two connecting rod portions 90 and 92 are connected by bolts 94. With the connecting rod bearing split at an angle of 45 the diameter of the annular crankcase walls can be reduced and still provide clearance between the bearing portions 92 and bolts 94 and the crankcase walls 32 and 36. With the connecting rod bearing portion split at the conventional angle of 90, the diameter of the crankcase walls has to be larger than shown to obtain the necessary clearance. Reduction of the diameter of the annular crankcase wall also reduces the volume of the connecting rod wells 40, resulting in increased crankcase pressures during engine operation, which pressures facilitate scavenging of the combustion products from the combustion chambers above the pistons.

The invention also provides four identical cylinder members 100, 102, 104 and 106 which can be diecast in the same mold. In the disclosed construction for an eight cylinder engine, each cylinder member has two wall portions detining cylinders 108 and 110 (FIG. 5).

As shown in FIG. l, the cylinder members 100, 102, 104 and 106 are each provided with two adjacently located fuel-air inlet passages 122 and 124, separated by a partition 125. As shown in FIGS. l, 5 and 8, the passages 122 and 124 open on the side of the cylinder members for connection to fuel-air intake manifolds, as hereinafter described. The walls defining the cylinders are provided with a series of fuel-air inlet ports and 132 (FIGS. 4 and 5) which communicate with the fuel-air inlet passages 122 and 124 and which are uncovered by the pistons during their upward stroke to permit the fuel-air inlet mixture to pass through the connecting rod well ports 41 into the connecting rod wells 40 in the crankcase 12. As shown in FIG. l, the fuel-air inlet passages 122 and 124 can be provided with reed valves 133 for controlling flow of the fuel-air mixture. The location of the reed valves 133 in the passages 122 and 124 results in quiet reed valve operation. Alternatively, the reed valves can be omitted by locating the fuel-air inlet ports 130 and 132 in the cylinder members so that the ports 130 and 132 are closed by the piston during the power stroke as shown in FIG. 4.

As shown in FIG. 5, each cylinder member is provided with two sets of exhaust apertures 134 and 136, one set for each cylinder. The sets of exhaust apertures 134 and 136 open into a common exhaust passage 138 between the two adjacently located cylinders. The exhaust passage 138 is separated from the fuel-air inlet ports 122 and 124 by a wall 139. Thus the fuel-air flow cools the wall 139 and the incoming fuel-air mixture is preheated to provide good combustion and economical operation.

The cylinder members 100, 102, 104 and 106 are each provided with fuel-air transfer passages 140 and 142 (FIGS. and 7) which are in the cylinder walls and which communicate with the ports 144 in the piston skirts 146 (FIG. l) to Provide fuel-air ow from the connecting rod wells 40 to the combustion chambers 148 above the pistons.

In accordance with the invention, means are provided for securing the crankcase sections together. In the disclosed construction, the means includes an outtured rectangular ange 150 (FIG. 1) on each of the cylinder members 100, 102, 104 and 106 with first through apertures 152 spaced around the ange 150. The outer faces 20, 21 and 26, 27 of the crankcase sections 14, 16 are provided with second through apertures 154 (FIG. 4) which are normal to the faces 20, 22, 26 and 27 and third threaded apertures 156 which open on interfaces 18 and 24. The apertures 152, 154 and 156 are desirably located in the same planes as the crankshaft bearings so the bearings take the loads when the crankcase sections 14 and 16 are compressed together. The crankcase sections 14 and 16 are aligned with tapered pins 158, which intert in the apertures 160 of each crankcase section 14 andf16 which are normal to the diagonal faces 18 and 24. The cylinder members 100, 102, 104 and 106 are clamped to the crankcase by bolts 164 which extend through apertures 152 in the flange 150 and apertures 154 in the crankcase sections 14 and 16 and are threadably received in apertures 156. The bolts 164 secure the cylinder members to the crankcase 12 and secure the crankcase sections 14 and 16 together to form an integral engine block.

As shown in FIGS. 8 and 9, when secured to the crankcase 12, the cylinder members are of varying heights or distances with respect to one end of the crankcase to accommodate the spaced crankpins on the crankshaft 31. The cylinder members are oriented so that the fuel-air inlet ports of two adjacent cylinder members are adjacently open to facilitate connection of the inlet ports to a common intake manifold 170 (FIG. 8), which has two passages 172, 174 separated by a central longitudinally extending partition 176. The intake manifold 170 can be connected to a dual carburetor 178 or to separate carburetors. Alternatively, independent manifolds for each fuel inlet passage can be used. When using diaphragm carburetors, the engine can be utilized with the crankshaft rotating about a horizontal, vertical or transverse axis. Since the fuel-air mixture introduced into each common connecting rod well is supplied from two carburetors, variation in adjustment of the fuel-air blend of each of the two carburetors will be balanced or blended by intermixing in the connecting rod wells to provide a uniform mixture for each pair of opposed pistons and cylinders.

The exhaust ports of each cylinder member 100, 102, 104 and 106 can be connected to exhaust manifolds 180 as shown in FIG. 9, with the lower ends of the exhaust manifolds extending into and anchored in the apertures 182 (FIG. 4) in the pedestal 17 of the crankcase 12. Adjacently located exhaust manifolds 180 can be connected to cross-over ducts (not shown), which can be connected to a common exhaust discharge tube (not shown). The exhaust manifolds can also be provided with water passages 184 to supply cooling water to a water jacket (not shown) in each of the cylinder members. The water passages in the exhaust manifold can communicate with water inlet ports 181 (FIG. 9) in the cylinders. Thus the incoming cooling water is pre-heated by the exhaust ilo-w to provide fast warmup for the cylinders. The exhaust manifolds also can be provided with cooling water return passages 186 for discharge of the cooling water.

In operation of the engine, and during one revolution of the crankshaft 31, the opposed cylinders fire in pairs with pistons 51 and 52 firing first, pistons 57 and 58 firing next, followed by pistons 53 and 54, then pistons 55 and 56. When the pistons of each pair of opposed pistons are at top dead center, the reduction in pressure or increase in vacuum in the crankcase wells 40 for the opposed pistons will cause the fuel-air mixture to be drawn from the fuelair manifolds 170 through the intake passages 122, 124 and fuel-air inlets and 132 and into the crankcase connecting rod Wells 40. When the pistons fire, they uncover the exhaust ports 134, 136 on the downstroke. As the pistons approach bottom dead center, the fuelair mixture is forced from the crankcase well 40` through the ports 144 in the piston skirts and into the transfer passages or 142 in the cylinder heads, which passages are open above the piston at this point of piston travel, whereby to fill the combustion chamber with the fuelair mixture and to assist in scavenging the combustion products to and through the exhaust ports 134 and 136. Upon movement of the piston toward top dead center, the transfer passage and exhaust ports 134 and 136 are closed and the fuel-air mixture is compressed prior to lgnition.

The invention provides a novel engine construction which can be utilized for a family of engines having a varying number of cylinders. For instance, a two cylinder engine can be constructed in which there are two opposed cylinder members on opposite crankcase faces with each cylinder member having a single cylinder and in which the crankshaft has two crankpins offset at A four cylinder engine can be constructed in accordance with the invention with four cylinder members with each cylinder member having a single cylinder. Each cylinder member is located on one of the four crankcase faces. A crankshaft with four crankpins is used with each crankpin offset at 180 from adjacent crankpins to form two crankshaft throws. Alternatively, a four cylinder engine can be constructed with two cylinders located on each of two adjacent faces.

The invention also provides an arrangement for securing the engine flywheel 200 to the crankshaft 31. In this regard, the ywheel 200 is provided with an aperture 202 which is defined by a tapered wall portion 204. The crankshaft 31 is provided with a tapered end portion 205 which interts in the aperture 202 of the flywheel.

The flywheel 200 is secured to the crankshaft 31 by a lock nut or fastener 206 which has an axially extending concentric boss 208 provided with an exterior thread 210. The fastener 206 can be provided with a hex head 212 which clamps the iiywheel 200 against the taper 205 on the crankshaft. The fastener 206 also includes a concentric axial aperture 214. The boss 208 is threadably received in a bore 216 at the end of crankshaft 31. The bore is provided with a threaded portion 218.

Means are provided for interconnecting the driveshaft 220 to the fastener 206 and to the crankshaft 31 to prevent relative movement of the fastener 206, the driveshaft 220, and crankshaft 31. As disclosed, the means includes an axial extension or projection 222 on the driveshaft 220. The extension 222 includes an external spline 224. The means also includes an internal spline 226 in the aperture 214 in the fastener 206, and an internal spline portion 228 in the bore 216 of the crankshaft 31 inwardly of the threaded portion 218. The spline 224 interfits in the spline 226 and the spline 228 to prevent the fastener 206 from unthreading during engine operation. Alternatively,

the projection or extension 222 on the driveshaft 220 can be provided with a key which interiits in a keyway in the fastener 206 and the bore 216 of the crankshaft. An extension on the crankshaft which is square in crosssection or any other geometric configuration which prevents relative rotary movement of the fastener 206, the driveshaft 220 and the crankshaft 31 could be used.

When the engine forms a part of a marine propulsion unit as shown in FIGS. 8 and 9, the flywheel 200 is located between the pedestal 17 on the crankcase and a similar flange 223 which forms a part of the lower unit driveshaft housing 232. Thus, the noise associated with cranking the engine caused by engagement of the gear 235 on the starter motor 234 (FIG. 8) with the teeth 236 on the flywheel 200 is confined between the pedestal 17 and the iiange 233 on the driveshaft housing 232 to provide a quiet starting operation.

The engine is secured to the driveshaft housing 232 by bolts 238 which clamp the flanges and 233 together. The bolts 239 which extend through apertures in flange 240 on the starter motor 234 also extend through the flange 233 to secure flanges 233 and 15 together.

As used in the claims, a pair of opposed oppositely acting pistons refers to a pair of pistons which are arranged so that the pistons are both at top dead center at the same time, are both at bottom dead center at the same time, and simultaneously move between top dead center and bottom dead center in opposite directions relative to each other.

Various of the features of the invention are set forth in the following claims.

What is claimed is:

1. An internal combustion engine comprising a crankshaft, a crankcase having first and second crankcase sections rotatably supporting said crank shaft, each of said sections being generally of triangular form with two exterior faces, and an interior face, and each having, at one end thereof, a ange extending generally at a right angle to said faces, said interior face of each section abutting along a plane extending through the axis of rotation of said crankshaft, and said interior faces of said sections each having opposed recessed wall portions to form common connecting rod wells, said flanges forming a pedestal generally perpendicular to said crankshaft for supporting said engine at one end thereof.

2. An engine in accordance with claim 1, wherein said crankshaft has two crankpins located in each of said connecting rod wells with said two crankpins being angularly offset at 180.

3. An engine in accordance with claim 1 wherein each of said crankcase sections has four opposed recessed wall portions to form four connecting rod wells.

4. An internal combustion engine comprising a crankcase having first and second crankcase sections with each section having two exterior faces each having two ports, and a third face, said faces abutting each other along a diagonal plane, and having opposed recessed wall portions forming common connecting rod wells each communicating with one port of each of said crankcase sections, a crankshaft rotatably supported in said crankcase with the axis of rotation thereof extending in said diagonal plane, said crankshaft having eight crankpins, respective connecting rods projecting through said ports and connected to said crankpins, a piston connected to each of said connecting rods, a cylinder member connected to each of said crankcase exterior faces, each of said cylinder members having wall portions defining two cylinders each receiving a different one of said pistons, each of said cylinder members including a common fuel-air intake passage, fuel inlet ports communicating between said cylinders and said intake passage, a common exhaust passage located between said cylinders, and exhaust ports passage, and means connecting said cylinder members to 8 said crankcase and connecting together said crankcase sections.

5. An engine in accordance with claim 4, wherein said means for securing said cylinder members to said crankcase and for securing together said crankcase sections comprises an outturned flange on each of said cylinder members, iirst through apertures in said tiange, second apertures extending from said outer faces of said crankcase sections, third apertures extending from said diagonal faces of said crankcase sections, fourth threaded apertures extending from said diagonal faces, pins which interlit in said third apertures of each crankcase section to align said crankcase sections and bolts extending through said first apertures, said second apertures and threadably received in said fourth apertures to secure said cylinder members to said crankcase.

6. An internal combustion engine comprising a crankcase having first and second crankcase sections, each of said sections generally having rst, second and third angularly related surfaces, means in each of said crankcase sections defining connecting rod well portions which are outwardly open on said third surfaces, said portions in each of said crankcase sections cooperating with the opposed connecting rod well portions to form common connecting rod wells, a pair of ports in each of said first and second surfaces of each of said crankcase sections, said ports in each of said first and second surfaces respectively communicating with differing ones of said connecting rod wells, means for securing said crankcase sections together with said third surfaces in abutting relation, a crankshaft rotatably supported in said crankcase, connecting rods extending through each of said ports into said connecting rod wells and connected to said crankshaft, pistons connected to each of said connecting rods to locate said pistons in opposed pairs and in oppositely acting relationship in each pair, said pairs of opposed oppositely acting pistons being reciprocal along axes offset at with respect to the axes of adjacent pairs of opposed oppositely acting pistons, said axes of said pairs of opposed oppositely acting pistons being spaced along the length of said crankcase, and a cylinder member for each of said first and second surfaces of each of said crankcase sections, said cylinder members each having means defining a pair of cylinders for receiving said pistons connected to said connecting rods extending through each of said ports into said connecting rod Wells.

7. An internal combustion engine comprising an engine block, a crankshaft rotatably supported in said engine block and having eight crankpins with each crankpin being angularly offset at with respect to the adjacent crankpin, said crankpins being aligned to define two coplanar crankshaft throws, eight pistons, connecting rods connecting said pistons to said crankshaft in opposed, oppositely acting pairs, wall means on said engine block defining eight cylinders, said cylinders being arranged with respect to said crankshaft to afford a stacked array of pistons with four of said pistons reciprocating about axes located in a first common plane, which plane intersects the longitudinal axis of said crankshaft and four other of said pistons reciprocating about axes located in a second common plane which intersects the longitudinal axis of said crankshaft and is at right angles with said first plane.

8. An engine comprising a crankcase, a plurality of pairs of opposed oppositely acting pistons movable relative to said crankcase, and a crankshaft in said crankcase and having a single crankpin for each piston, each crankpin being angularly offset at 180 from each adjacent crankpin and being connected to a separate one of said pistons.

9. An internal combustion engine in accordance with claim l, including a iiywheel having an aperture for receiving said crankshaft, a driveshaft, a fastener having an axially extending boss and an axial aperture, said boss having an exterior thread and said crankshaft having a bore, a portion of said bore being threaded for threadably receiving said -boss of said fastener, and means for interconnecting said crankshaft, said driveshaft and said fastener to prevent relative rotary movement of said fastener, said driveshaft and said crankshaft.

10. The device of claim 9, wherein said means for interconnecting said driveshaft, said fastener and said crankshaft to prevent relative rotary movement of said fastener, said driveshaft and said crankshaft, comprises a coaxial extension on said driveshaft, said extension being provided with an external spline, an internal spline in said aperture in said fastener which interfits :with said spline on said extension of said driveshaft, and an internal spline in said lbore in said crankshaft intertting with said external spline on said extension of said driveshaft.

11. The device of claim 9, wherein said crankshaft has a tapered shoulder, and wherein said aperture in said flywheel is dened by a tapered wall which interts with said tapered shoulder on said crankshaft and a head on said fastener to engage said flywheel and clamp said flywheel against said tapered shoulder on said crankshaft.

12. An engine in accordance with claim 8 wherein said crankcase has a length less than the sum of the product of the total number of pistons times the diameter of one piston divided by two, plus the diameter of one piston.

13. An engine in accordance with claim 8 including bearings rotatably mounting said crankshaft in said crankcase, said bearings and said crankpins having axes in coplanar relation to one another.

14. An internal combustion engine comprising a crankcase having first and second crankcase sections each of generally triangular form including two exterior faces, and an interior face, said interior faces being in abutting relation to each other and each including opposed recess wall portions forming connecting rod wells, said crankcase sections also each including, at one end thereof, a llange extending generally at a right angle to said faces, said anges forming a pedestal for supporting said engine at one end thereof, a plurality of pairs of oppositely acting opposed pistons movable relative to said crankcase, and a crankshaft mounted in said crankcase in generally perpendicular relation to said anges and with the rotational axis thereof located generally at the juncture of said interior faces and having a single crankpin for each piston, each crankpin being angularly offset at from each adjacent crankpin and being connected to a separate one of said pistons.

15. An internal combustion engine comprising a crankcase having first and second crankcase sections each of generally triangular form including two exterior faces, and an interior face, said interior faces being in abutting relation to each other and each including opposed recessed wall portions forming common connecting rod wells, a plurality of pairs of oppositely acting opposed pistons movable relative to said crankcase, and a crankshaft mounted in said crankcase with the rotational axis thereof approximately at the juncture of said interior faces, said crankshaft having a single crankpin for each piston, each crankpin being angularly offset at 180 from each adjacent crankpin and being connected to a separate one of said pistons.

References Cited UNITED STATES PATENTS 1,708,901 4/1929 Royce 123-56(A3) 1,713,759 5/1929 Irwin 12s- 55(A) 2,076,892 4/1937 Irgens 12s-56031) 2,318,599 5/1943` Davis 123 55(A) FOREIGN PATENTS 81,671 11/1919 switzerland 123-56(A) WENDELL E. BURNS, Primary Examiner U.S. Cl. X.R.

92-148, 261; l23-56AA, 56BA, 192R, 195R.

gg@ UNITED STATES PATENT OFFICE l CERTIFICATE 0F CORRECTION Patent NO- 3 z 605 s 705 Dated September l() 1 Q] Inventor(s) Kgrt E, Ziegler It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 7, line 56 after "said", insert (SEAL) Attest.:

Amami@ @miem ROBERT GOTTSCHALK Commissioner' of Patents 

